Page:Concepts for detection of extraterrestrial life.djvu/57

Rh action time, the excitation lamps are turned on sequentially and the light signal, or fluorescent level in the case of the phosphatase assay, is detected by the photomultiplier tube. This information is then reduced to digital form and transmitted. One reading per chamber every 15 minutes would be satisfactory, requiring a fraction of a bit per second for telemetry. Certain chambers of the instrument are designed so that they will not collect soil. This permits a comparison of the behavior of the solvent-substrate mixtures subjected to the same conditions of voyage and Martian environment with the results from those reaction chambers receiving dust samples. This helps to ensure that the information concerning a sign of life is not due to a faulty test.

Modular design of the multivator offers several advantages. First, the entire multivator becomes potentially more reliable with 15 independently operated modules. Secondly, each module may be filled with different types of solvents, thereby increasing the range of experiments that can be performed with a single multivator package. Thirdly, the modular design allows more flexibility in making the final choice of the actual experiment to be performed. It also permits postponing this choice to a relatively short time before the launch date of the mission. More than a full complement of modules could be under design and development; postponement of final choice would not interfere with orderly spacecraft development and construction as long as the experiments met the very simple interface parameters characteristic of the multivator experimental modules.